A re-appraisal of species diversity within the Australian grasswrensAmytornis(Aves: Maluridae)

2013·0.29 MB·English

by  Les Christidis

A re-appraisal of species diversity within
Amytornis
the Australian grasswrens (Aves:
Maluridae)
Les Christidis1,2*, Frank E. Rheindt3, Walter E. Boles4,
Janette A. Norman4
1National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW 2450, Australia
2Department of Genetics, University of Melbourne, Parkville, Vic. 3052 Australia
3Department of Biological Sciences, National University of Singapore, Singapore
4Division of Research and Collections, Australian Museum, 6 College St, Sydney, NSW 2010, Australia
*Corresponding author: [email protected]
The Australian grasswrens (Amytornis) comprise a genus of cryptically plumaged species inhabiting
the arid regions of southern, western, central, and northern Australia. Isolated, fragmented
T populations characterise the distributional pattern of several species, whereas others appear to
show ecophenotypic clinal variation in plumage patterns. These features have made the species-level
C
taxonomy of the genus a matter of ongoing debate. We undertook qualitative considerations of
A
morphological, biogeographical and ecological features in combination with quantitative DNA distance
measures from published studies, to provide a comprehensive species level revision of Amytornis. In
R
addition to the ten species recognised by Schodde and Mason (1999) (housei, textilis, goyderi, purnelli,
T
ballarae, merrotsyi, woodwardi, dorotheae, striatus, barbatus), we also recognise as species the following:
S modestus, rowleyi, oweni and whitei. These fourteen species are placed into four subgenera: Amytornis,
B Magnamytis, Maluropsis and Cryptamytis subgen. nov. The latter subgenus is erected for A. merrotsyi. The
potential impacts that this new taxonomy will have on the conservation status of the various taxa
A
are canvassed.
Key words: grasswrens, molecular systematics, avian taxonomy, conservation status
http://dx.doi.org/10.7882/AZ.2013.004
Introduction
The Australian grasswrens (Amytornis) comprise a genus of 1997 and 1998, the range of A. merrotsyi (Short-tailed
cryptically plumaged species inhabiting the arid regions of Grasswren) was extended to include the Gawler Ranges,
southern, western, central and northern Australia (Rowley South Australia (SA) (Baxter and Paton 1998) and this
and Russell 1997, 2007). Isolated fragmented populations population was later described as a new subspecies A. m.
characterise the distributional pattern of several species pedleri (Christidis et al. 2008).
whereas others appear to show ecophenotypic clinal variation
A good understanding of the species composition of
in plumage differentiation (see Schodde and Mason 1999).
Amytornis is yet to be established. Schodde and Mason
The combination of subtle patterns of plumage variation,
(1999) provided an excellent framework of morphological
fragmented populations and clinal variation have made the
differentiation in the genus but acknowledged that
species-level taxonomy of the genus a matter of ongoing
the species status of several taxa required further
debate (e.g. Parker 1972; Mayr 1986; Schodde 1982a,b;
investigation. They recognised ten species (A. housei
Schodde and Mason 1999; Christidis and Boles 2008;
Black Grasswren, A. textilis Thick-billed Grasswren, A.
Christidis et al. 2010; Black et al. 2010).
goyderi Eyrean Grasswren, A. purnelli, A. ballarae, A.
Several species of grasswren occur in remote areas
merrotsyi, A. woodwardi White-throated Grasswren, A.
of arid Australia and it is not surprising that new
dorotheae Carpentarian Grasswren, A. striatus Striated
species, subspecies and populations have continued to
Grasswren, A. barbatus). More recently, there has been
be discovered. For example, Amytornis barbatus (Grey
a trend to treat A. textilis (Western Grasswren) and A.
Grasswren) was first described in 1968 by Favaloro and
modestus (Thick-billed Grasswren) as separate species (e.g.
McEvey (1968) and the subspecies A. b. diamantina was
Black 2004; Black et al. 2010). The distributions of the
described 19 years later (Schodde and Christidis 1987).
species and subspecies of Amytornis discussed in this paper
Condon (1969) described the subspecies A. textilis ballarae
are depicted in Figures 1, 2 and 3.
from western Queensland (Qld), which was later included
by Parker (1972) within A. purnelli (Dusky Grasswren), Christidis et al. (2010) examined DNA distances and
before being elevated to species status by Schodde and relationships for all currently recognised species and most
Mason (1999) as A. ballarae (Kalkadoon Grasswren). In subspecies of Amytornis. Although their study had major
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2013 429
Zoologist volume 36 (4)
Christidis et al.
Figure 1. Distribution of Amytornis
purnelli, A. ballarae, A. housei, A. goyderi
and A. merrotsyi. Based on Schodde
and Mason (1999)
Figure 2. Distribution of Amytornis
striatus, A. oweni, A. whitei, A. rowleyi,
A. woodwardi and A. dorotheae. Based
on Schodde and Mason (1999)
Australian
443300 Running foot 2013
Zoologist volume 36 (4)
Species level taxonomy of grasswrens
Figure 3. Distribution of Amytornis
textilis, A. modestus and A. barbatus.
Based on Schodde and Mason
(1999)
taxonomic implications, this was not the focus of the The DNA study of Christidis et al. (2010) provides a sound
paper, and no taxonomic recommendations were made. framework on which to apply the DNA-based criteria of
Here we interpret the levels of DNA differentiation Bradley and Baker (2001) in determining species limits
recorded by Christidis et al. (2008, 2010) and Austin within Amytornis. The three mitochondrial genes ND2,
et al. (2013) in context with published morphological, ND3 and CO1 fit the criteria of stable, constantly
biogeographical and ecological features (e.g. Schodde evolving coding genes and have been successfully used
and Mason 1999; Black 2004, 2011a,b; Black et al. 2010) to define genus and species limits in other Australian
to provide a comprehensive species and subspecies level songbird families (Norman et al. 2007; Jønsson et al. 2008;
revision of Amytornis. Driskell et al. 2011; Christidis et al. 2011). Although
Christidis et al. (2010) lacked DNA data for A. striatus
whitei, the coverage of all other taxa in this complex allows
Methods
its taxonomic status to be discussed in a relative context.
Taxonomic decisions based on mitochondrial DNA
The taxa under consideration here have been defined
(mtDNA) differentiation are best made in the context
at species and subspecies levels based on plumage,
of the level of distances separating well-established
morphology and ecology by Schodde and Mason (1999),
species on a genus-by-genus basis, in order to account
Black (2004) and Black et al. (2010).
for differing evolutionary rates (e.g. Norman et al. 1998;
Bradley and Baker 2001; Baker and Bradley 2006;
Results and Discussion
Garnett and Christidis 2007; Christidis and Norman
2010). Bradley and Baker (2001) outlined five criteria DNA differentiation and species taxonomy
that needed to be met by DNA studies in order to
of Amytornis
assess reliably species status of taxa: (1) phylogenetic
methods employed to test genetic distance patterns; Applying a mtDNA-distance approach to species status
(2) use of stable and constantly evolving coding genes; assessment requires comparison with the lowest mtDNA
(3) inclusion of known species-level “bench marks” for divergences recorded between well-accepted sister
evaluating different levels of sequence divergence; (4) species (Norman et al. 1998; Garnett and Christidis
comparisons restricted to single speciation events; and 2007; Christidis and Norman 2010). According to the
(5) comprehensive inclusion of sister taxa. DNA phylogeny for Amytornis (Christidis et al. 2010),
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Christidis et al.
the most relevant distances are those recorded between Amytornis woodwardi and A. dorotheae
Amytornis woodwardi and A. dorotheae which were 2.6%
Condon (1951) combined A. woodwardi (White-throated
for ND2 and ND3, and 1% for CO1 (Table 1). At the
Grasswren) and A. dorotheae (Carpentarian Grasswren)
other extreme, the sister species A. ballarae and A. purnelli
as a single species, and on the basis of the low levels of
differed by 7.6%, 5.7% and 4.2% for ND2, ND3 and CO1
mtDNA differentiation recorded between the two (2.6%
respectively (Table 1). Within-species calibrations are
for ND2 and ND3, and 1% for CO1; Table 1), this might
provided by A. barbatus where distances between the two
appear to be appropriate. Nevertheless, the two differ
subspecies (barbatus and diamantina) were 1.8%, 1.2%
greatly in overall morphology (Schodde and Mason 1999;
and 1.5% for ND2, ND3 and CO1 respectively (Table
Higgins et al. 2002). In terms of plumage patterns and size,
1), and A. merrotysi where the ND3 distance between the
A. woodwardi more closely resembles A. housei whereas
two subspecies was 2.1%. Within-taxon variation was not
A. dorotheae is more similar to A. striatus. There are also
evaluated by Christidis et al. (2010). However, Christidis
subtle differences in habitat preferences (summarised in
et al. (2008) recorded intra-subspecific ND3 genetic
Higgins et al. 2002). The optimal habitat for A. woodwardi
distances of 0.6% and 0.9% within A. merrotsyi pedleri and
is flat, unbroken plateaux that are sparsely vegetated with
A. m. merrotsyi, respectively.
Triodia hummocks. In the north of its range, A. dorotheae
Based on these comparisons (Table 1), and the criteria occurs in dissected plateaux and slopes with Triodia
advocated by Norman et al. (1998) and Bradley and Baker hummocks whereas in the south it occurs in less dissected
(2001), we argue that within Amytornis, DNA distances siltstone ranges, with Triodia cover. Two taxonomic
for ND2, ND3 and C01 of approximately 2% or less are options are possible here. First, the extent of plumage
reflective of subspecies-level recognition. Species-level and ecological differences are ignored and the two taxa
distances are more gene specific, with CO1 being the are combined based on low DNA divergence. Conversely,
slowest diverging gene. The minimum DNA distance the DNA distances are interpreted as representing recent
between the sister species A. ballarae and A. purnelli was speciation. Christidis and Norman (2010) argued that
4.2%. Consequently, distances above 4% can be argued low levels of DNA differentiation, on their own, are not
to be reflective of species-level recognition in Amytornis. sufficient to combine taxa and this approach is taken
Species that fall in this well differentiated category were here. Consequently, we here retain A. woodwardi and A.
A. housei, A. goyderi, A. purnelli, A. ballarae, A. merrotsyi dorotheae as recently evolved species.
and A. barbatus.
Amytornis modestus and A. textilis
There were three cases where DNA distances between
taxa within genetically well-defined complexes fell in Schodde and Mason (1999) treated Amytornis modestus
the range of 2–4%: (1) Amytornis woodwardi and A. (Thick-billed Grasswren) as a subspecies of A. textilis
dorotheae; (2) Amytornis modestus and A. textilis; and (3) A. (Western Grasswren), although the two had been kept
striatus. Here, more detailed morphological and ecological separate by Schodde (1982b). The pattern of mtDNA
considerations are discussed below in order to determine distances recorded for the complex by Christidis et al.
the number of species in each complex. (2010) is more consistent with species-level status for both
Table 1. mtDNA divergences based on Kimura distances (Kimura 1980). Species recognition and composition of the
subgenera follows the revision advocated in the current study: Amytornis (housei, textilis, modestus, goyderi, purnelli, ballarae);
Magnamytis (woodwardi, dorotheae, striatus, rowleyi, oweni, whitei); Cryptamytis (merrotsyi); and Maluropsis (barbatus).
mtDNA gene region
Comparisons ND2 ND3 CO1
Between subgenera
Amytornis – Magnamytis 12.6%-15.45% 10.6%-14.2% 6.7%-10.8%
Amytornis – Cryptamytis 14.2%-16.3% 11.6%-14.4% 8.4%-10.2%
Amytornis – Maluropsis 15.3%-17.6% 12.5%-15.1% 9.2%-10.8%
Magnamytis – Cryptamytis 13.6%-13.8% 9.6%-10.9% 8.1%-10.7%
Magnamytis – Maluropsis 13.8%-15.2% 8.2%-12.5% 10.4%-11.5%
Cryptamytis – Maluropsis 16.0%-16.3% 11.8%-12.5% 9.0%-9.2%
Between closely related and sister taxa
A. ballarae v A. purnelli 7.6% 5.7% 4.2%
A. textilis v A. modestus 4.4% 3.5% 4.0%
A. textilis textilis v A. t. myall 0.4% 1.7% 1.2%
A. textilis myall v A. modestus 4.8% 2.9% 4.4%
A. striatus v A. rowleyi 4.0% 4.5% 3.8%
A. striatus v A. oweni na 4.2% na
A. dorotheae v A. woodwardi 2.6% 2.6% 1.0%
A. merrotsyi merrotsyi v A. m. pedleri na 2.1% na
A. barbatus barbatus v A. b. diamantina 1.8% 1.2% 1.5%
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Species level taxonomy of grasswrens
forms. The north-easterly form A. modestus differed by up Although DNA data is not available for inexpectatus,
to 4.8% (ND2) from A. t. myall and 4.4% (ND2) from A. it is very similar to adjacent obscurior in appearance.
t. textilis. Comparable distances were also evident in ND3 On the available morphological and genetic evidence
and CO1 (Table 1). Black et al. (2010) and Black (2004) a conservative, but robust, treatment of subspecies in
presented detailed arguments based on a consideration of A. modestus would recognise two forms: (1) modestus
plumage, morphology and habitat preferences for treating (including indulkanna) west of Lakes Eyre and Torrens
A. modestus as separate species to A. textilis, with myall extending north to the MacDonnell Ranges; (2) and
being aligned with the latter. This alignment is consistent inexpectatus (including raglessi, curnamona, obscurior and
with the DNA data of Christidis et al. (2010). DNA the population from northeast of Lake Eyre) to the east
distances between A. t. textilis (Western Australia [WA]) and extending into NSW. Further research is needed to
and A. t. myall (northern Eyre Peninsula, SA) ranged assess whether the shallow phylogeographic structure
from 0.4% to 1.7% (Table 1) and these are comparable separating indulkanna and nominate modestus represents
to those recorded between subspecies of A. barbatus population subdivision or subspecific differentiation.
and A. merrotsyi (Table 1). The two are also similar in
A further question that needs to be addressed is whether
plumage and morphology (Schodde 1982a; Schodde
further subspecies are recognisable within A. textilis textilis.
and Mason 1999; Black 2004). Black (2004) advocated
Black (2011b) reassessed the taxonomic history of the
use of the vernacular names Western Grasswren and
complex and analysed morphometric measurements of
Thick-billed Grasswren for A. textilis and A. modestus
23 to 27 individuals. Based on this sample he further
respectively, which is in keeping with previous usage.
divided A. t. textilis into four subspecies: textilis, carteri,
North (1902) gave the name Thick-billed Grasswren to
giganturus and macrorous (including varius and morgani).
Amytis modesta when he originally described that taxon,
The morphological analysis of Black (2011b) was
while the name Western Grasswren has previously been
limited due to small sample sizes. Reinstatement of the
applied to Amytornis textilis (RAOU 1926; Parker 1972).
southern form giganturus was based on only 3 individuals
Black (2011a) recognised seven taxa within A. modestus, and it was argued that they were darker and larger
of which six were formally treated as subspecies. Four than northern populations, but this could equally be
of these taxa referred to previously named subspecies reflective of ecophenotypic variation. Black (2011b) also
(modestus, indulkanna, inexpectatus, obscurior), two were acknowledged that the reported darker plumages in carteri
newly described (2011a) (raglessi, curnamona), and the were only apparent in specimens from the HLW collection
population from northeast of Lake Eyre was mooted as (Museum Victoria).
a possible unnamed seventh subspecies. This revision
In their DNA study Austin et al. (2013) found only
was primarily based on plumage and morphological
minor levels of genetic divergence within A. t. textilis. Two
analyses. Specimens from the two NSW taxa (inexpectatus,
subgroups were recognised. The first comprised textilis and
obscurior) were not examined. When summarising the
carteri from the Shark Bay region and Dirk Hartog Island,
plumage and morphological data used to define modestus,
while the second comprised macrorous and giganturus from
indulkanna, raglessi and curnamona, Black (2011a)
southern WA and southern SA. A case could be made for
acknowledged that the differences were relatively slight
recognising two subspecies A. t. textilis (including carteri)
and that the presence or absence of sexual dimorphism
and A. t. macrorous (including giganturus). Given that
was especially fraught, given the limited samples of female
the genetic distances separating the two groups are more
specimens for some populations. An examination of the
equivalent to levels recorded within subspecies, we refrain
plumage based Scatterplot depicted in Black (2011a:
from recognising them as subspecies at this stage.
Fig. 5) reveals that almost all the variation observed
in curnamona is circumscribed by that observed within A. striatus complex
raglessi. Furthermore, one of the defining bill characters
The Amytornis striatus complex comprises several
for curnamona is described as “variably finer bill”, which
isolated forms. Schodde and Mason (1999) segregated
is more suggestive of ecophenotypic variation rather than
the central Queensland population as a new subspecies,
taxonomic diversity. Differences between raglessi and
rowleyi, distinguished by its small size and russet plumage.
curnamona from South Australia and the adjacent NSW
In genetic distances, rowleyi differs from nominate
forms inexpectatus and obscurior were not evaluated by
striatus by 3.8–4.5% across the three mitochondrial genes
Black (2011a), except to note strong plumage similarities
(Table 1). This divergence is higher than that observed
between them.
for subspecific differentiation and more comparable
Austin et al. (2013) examined mitochondrial differentiation with that recorded between A. modestus and A. textilis.
in all forms of A. modestus recognised by Black (2011a) and The form rowleyi is geographically isolated, being
identified an eastern and western clade that differed by a restricted to the Cooper–Diamantina drainage and over
genetic distance of 1.7%. The western clade comprised 600 km distant from other populations of striatus (based
the forms modestus and indulkanna, and the eastern clade on Barrett et al. 2003). The geographical isolation in
comprised obscurior, raglessi, curnamona and the unnamed combination with the genetic distances is indicative of
‘eyre’ form. The most easterly extinct form inexpectatus was a long-independent evolutionary trajectory for rowleyi
not examined. There was no phylogeographic structure in relative to nominate striatus. When taken in context
the eastern clade, whereas the western clade had two with the morphological and plumage differentiation
subgroups that differed by a genetic distance of 0.5%. (Schodde and Mason 1999), we conclude that the
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Zoologist volume 36 (4)
Christidis et al.
form rowleyi is best treated as a separate species to A. Subgenera within Amytornis
striatus. Amytornis rowleyi is a newly elevated species
Schodde and Christidis (1987) erected the subgenus
with no previous vernacular name. Consequently, we
Maluropsis for Amytornis barbatus arguing that it was
apply the name Rusty Grasswren in reference to its
basal to all the other species in Amytornis. This assertion
russet plumage.
was based on considerations of plumage pattern and
Excluding rowleyi, there has been considerable debate preliminary protein allozyme data. Following on from
on how many other forms exist within the A. striatus
this, Schodde and Mason (1999) placed all other
complex. Mayr (1986) recognised three forms: (1) whitei
species of Amytornis into the nominate subgenus. In
in the Pilbara of WA, which is large and rufous; (2) oweni
contrast, the DNA data of Christidis et al. (2010)
in the sand deserts of WA, SA and the Northern Territory
consistently identified four equally diverged lineages
(NT), which is small and rufous but with a white belly;
within Amytornis: (1) barbatus; (2) ballarae, purnelli,
and (3) striatus in the south-eastern Australian mallee
goyderi, textilis–modestus, housei; (3) dorotheae, woodwardi,
through to central New South Wales (NSW), which is
striatus; and (4) merrotsyi. DNA distances between
large and grey-brown. Condon (1951), Keast (1958),
subgenera (Table 1) ranged from 12.6% to 17.6%
Mees (1961) and Ford and Parker (1974) combined the
(ND2), 8.2% to 15.1% (ND3) and 6.7% to 11.5%
first two whereas Schodde (1982a) and Schodde and
(CO1). Furthermore, the DNA phylogeny of Christidis
Mason (1999) combined the latter two. Christidis et al.
et al. (2010) indicated that the four lineages diverged in
(2010) provided ND3 DNA data for A. striatus oweni. The
rapid succession from each other, and that if subgenera
DNA distances between A. s. oweni and A. s. striatus and
are recognised then these should correspond with each
A. rowleyi were 4.2% and 4.5% respectively. These levels
of the lineages. This is the action that is recommended
are comparable to species-level recognition as defined
here. In addition to Maluropsis (lineage 1) and Amytornis
previously for Amytornis.
(lineage 2), the name Magnamytis Mathews, 1912 is
Although Schodde and Mason (1999) argued that available for lineage 3. No subgeneric name is available
plumage differences between oweni and nominate striatus
for lineage 4. Accordingly we here distinguish a new
are clinal, they point out that the available specimen
subgenus for Amytornis merrotsyi.
material is meagre and the interpretation is provisional.
Amytornis subgenus Cryptamytis, subgen. nov. Christidis,
Furthermore, such a cline does not fit in with the large
Rheindt, Boles and Norman, this study
distributional break between the two taxa, which includes
the biogeographically significant Eyrean and Murravian Type species: Amytornis merrotsyi Mellor, 1913
Barriers in south-eastern SA. Accordingly, A. oweni is
Diagnosis: Face patterned with an obscure supra-loral bar
recognised here as a species with the vernacular name
and vestigial black malar stripe. Tail is disproportionately
Sandhill Grasswren in reference to its preferred habitat.
short.
The vernacular name Striated Grasswren is restricted to
the nominate form in the mallee regions of SA, Victoria Etymology: The original generic name Amytis Lesson,
(Vic) and central NSW. Further work, including DNA 1831 was shown to be preoccupied and so was replaced
analysis, is required to assess the status of the “transitional by Amytornis Stejneger, 1885. Cryptamytis combines
populations” around the northern Eyre Peninsula kruptos, (Greek, hidden) and amytis, from the original
identified by Schodde and Mason (1999). These could name (that of a Persian princess). The name is figuratively
represent ecophenotypic variants or a separate subspecies ‘secret princess’ alluding to the bird’s secretive habits and
within A. oweni (as defined here). long hidden identity.
DNA data are not available for the form A. striatus Taxonomic revision of Amytornis
whitei, which is restricted to the Pilbara region of
WA. Nevertheless, we believe that it also represents In considering the DNA, plumage, morphological,
a separate species for two reasons. First, it is the most ecological and geographical data, we here divide the genus
morphologically distinct member of the A. striatus Amytornis into four subgenera comprising 14 species.
complex (Schodde and Mason 1999). Secondly, it is the Four of these species are further divided into subspecies.
only member of the complex to inhabit rocky outcrops; The shallow phylogeographic structure recorded by
all other members inhabit flatlands. Given that no other Austin et al. (2013) in A. textilis textilis and A. modestus
species of Amytornis occurs in both rocky outcrops modestus is here interpreted as representing population
and flatlands, it is highly unlikely that the form whitei subdivision rather than subspecific differentiation. With
is conspecific with A. oweni, the geographically most this caveat we propose the following taxonomy for the
proximate member of the complex. Schodde and Mason genus Amytornis:
(1999) in fact suggested that the significance of this
Amytornis Stejneger, 1885
habitat differentiation needed be further investigated
as it could point to sibling species status. Furthermore, Maluropsis Schodde and Christidis, 1987
species of Amytornis have been found to be tightly
A. barbatus Grey Grasswren
definable in terms of habitat preferences (Christidis
et al. 2010). Accordingly, we recognise A. whitei as a A. b. barbatus
separate species and apply the vernacular name Pilbara
A. b. diamantina
Grasswren in reference to its geographical isolation.
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Zoologist volume 36 (4)
Species level taxonomy of grasswrens
Magnamytis Mathews, 1912 sequence data (Christidis et al. 2010) confirmed that
A. merrotsyi represents a monospecific lineage which is
A. woodwardi White-throated Grasswren
formally recognised here as the subgenus Cryptamytis.
A. dorotheae Carpentarian Grasswren Under a phylogenetic diversity approach, A. merrotsyi
A. striatus Striated Grasswren has the same conservation value as the other three
Amytornis subgenera Amytornis, Magnamytis, and
A. whitei Pilbara Grasswren
Maluropsis with six, six and one species respectively.
A. oweni Sandhill Grasswren In terms of phylogenetic diversity status, the
A. rowleyi Rusty Grasswren conservation value of A. merrotsyi has increased as a
result of its placement in a new subgenus. However,
Cryptamytis subgen nov
there has been no change to its actual conservation
A. merrotsyi Short-tailed Grasswren status in terms of threats.
A. m. merrotsyi A second taxonomic change advocated that has major
conservation implications concerns the status of the forms
A. m. pedleri
oweni and striatus within the Amytornis striatus complex.
Amytornis Stejneger, 1885
Schodde (1982a) and Schodde and Mason (1999)
A. ballarae Kalkadoon Grasswren treated oweni and striatus as a single form, in contrast
to Mayr (1986), who kept them as separate subspecies.
A. purnelli Dusky Grasswren
Garnett et al. (2011) followed the arrangement of
A. goyderi Eyrean Grasswren Schodde and Mason (1999), and subsequently listed A.
A. housei Black Grasswren s. striatus as ‘Near Threatened’. This listing took into
consideration the wide geographical range of the taxon
A. textilis Western Grasswren
stretching from WA through to NSW. According to
A. t. textilis (includes carteri, giganturus and macrorous)* Garnett et al. (2011), “the habitat in the south-east of
the subspecies’ range has been historically reduced and
A. t. myall
fragmented, and such losses continue at a slow rate in
A. modestus Thick-billed Grasswren
NSW”. According to the taxonomy adopted here, this
A. m. modestus (includes indulkanna)* latter region corresponds to the distribution of A. striatus
sensu stricto. Clearly a reappraisal of the conservation
A. m. inexpectatus (includes raglessi, curnamona and
status of A. striatus as defined here is required. The
obscurior)*
western form A. oweni is more widespread and the ‘Near
* Subspecific composition may require further assessment Threatened’ listing may still be applicable but this also
needs to be revisited.
Conservation implications
In their assessment of conservation status, Garnett et al.
The taxonomic revision outlined here has several
(2011) accepted the taxonomy proposed for Amytornis
conservation implications. At the higher end are
modestus by Black (2011a). The western forms modestus
considerations of phylogenetic diversity. Erwin
and indulkanna were listed as ‘Extinct’ and ‘Least Concern’,
(1991) and Vane-Wright et al. (1991) argued that
respectively. Here the two are kept in modestus which
conservation priorities should take into consideration
would now be listed as ‘Least Concern’. The eastern
the phylogenetic or evolutionary distinctiveness of
forms inexpectatus, raglessi, curnamona and obscurior were
the taxa under consideration. Higher priority would
listed as ‘Extinct’, ‘Vulnerable’, ‘Near Threatened’ and
be given to taxa belonging to ancient or species-
‘Critically Endangered’, respectively. Given that they are
poor groups because these contribute more to overall
all treated here under inexpectatus, a reappraisal of the
taxonomic diversity. Several approaches to measuring
conservation status of this taxon is also required.
phylogenetic diversity have been proposed (e.g. Faith
1992; Krajewski 1994). A common theme in each of Black (2011b) divided Amytornis textilis textilis into four
these approaches is that the phylogenetic relationships subspecies with only the nominate form being extant.
of a taxon directly influence its conservation priority Consequently, the conservation implications for the
ranking. As such, taxonomic revision can have a extant populations will not change irrespective of whether
significant bearing on conservation ranking. one or more subspecies are recognised in this complex.
The case of Amytornis merrotsyi provides an Garnett et al. (2001) listed Amytornis barbatus diamantina
interesting case study. Although originally described as ‘Least Concern’ and A. b. barbatus as ‘Endangered’.
as a new species (Mellor 1913), the Chestnut- They noted that the subspecific identity of populations
mantled Grasswren, it was subsequently included as from south-western Queensland and South Australia,
a subspecies of A. striatus (e.g. Keast 1958; Parker while assumed to belong to diamantina (Schodde
1982; Schodde 1982a), before again being elevated 1990), required further confirmation (Carpenter
to species status on the basis of genetic (Christidis 2002). However, Christidis et al. (2010) demonstrated
1999) and morphological (Schodde and Mason 1999) that genetically, these populations were aligned with
assessments. The latter considered it part of the A. diamantina as argued by Schodde (1990). This taxonomic
striatus group whereas the former identified it as a resolution does not affect the current conservation
distinct lineage. Mitochondrial and nuclear DNA status of either subspecies.
Australian
2013 435
Zoologist volume 36 (4)
Christidis et al.
Acknowledgments
Andrew Black, Harry Recher, Richard Schodde and two subgenus. Special thanks to Caroline Blackmore for
anonymous referees provided thoughtful and valuable producing the figures. The study was supported by grants
comments on the manuscript. We are especially grateful from the Australian Biological Resources Survey and the
to Andrew Black for input into the name of the new Norman Wettenhall Foundation.
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